Conventionally, the white tone of the white decorative parts, for example, wristwatch parts, such as wristwatch bands, and spectacle frames is provided by forming a metal coating, such as a titanium carbide or platinum coating, as an outermost layer according to a wet or dry plating technique.
For example, in Japanese Patent Laid-open Publication No. 60(1985)-141868, a wristwatch armoring part is proposed which comprises a metal substrate, a phosphorus-containing nickel layer formed on the surface of the metal substrate by plating so as to have a thickness of 10 to 200 .mu.m and hardened and a silvery white coating of titanium carbide or oxide formed on the surface of the nickel layer according to an ion plating process.
However, this titanium carbide coating formed on the surface of the wristwatch armoring part has a silvery white lacking both of lightness and warmth. Further, the production of this wristwatch armoring part has a drawback in that it is difficult to stably form a silvery white coating of titanium carbide or oxide.
The same applicant as in the present application proposed white personal ornaments (for example, spectacle frames and wristwatches) each comprising a surface layer of a platinum or platinum alloy coating in Japanese Patent Laid-open Publication No. 3(1991)-120355.
However, this platinum or platinum alloy coating of each of the white personal ornaments has a gray white giving an impression of coldness to the lookers and lacking warmth.
Therefore, in the art, there is a demand for the developments of a white decorative part having an appearance of superiority quality which comprises an outermost coating having a white tone of high lightness and warmth formed according to a dry plating process, a white decorative part which can be mass-produced while stably maintaining the white tone of warmth and a process for producing the same.
Some types of metals may cause a skin rash attributed to metal allergy. Therefore, there is also a demand in the art for the developments of a white decorative part free from the danger of causing metal allergy and a process for producing the same.
Accordingly, an object of the present invention is to provide a white decorative part having an appearance of superiority quality which comprises an outermost coating having a white tone of high lightness and warmth formed according to a dry plating process. Another object of the present invention is to provide a white decorative part having the above characteristics which does not cause dermatitis attributed to metal allergy.
A further object of the present invention is to provide a process for producing a white decorative part which can be mass-produced while stably maintaining the white tone of high lightness and warmth. Still a further object of the present invention is to provide a process for producing a white decorative part having the above characteristics which does not cause dermatitis attributed to metal allergy.